Marginal Necrosis aka edge burn

[flipflop64]

Hi guys,
Every grow i see the same problem
Marginal Necrosis
I dont know if it's nutrient burn, calcium def or Potassium def. I had the same problem last grow (before that never).
I am feeding 3EC Athena Pro, 6PH
Feed two times a day, once after lights turn on and once mid day.
Pushing 30% drybacks on day 41

 

[Fromunda506]

Potassium. Tips and serrations give it away. No way she actually needs k with that feed schedule. my gut is early lockout from a bit of overfeeding plus drybacks. if you overshoot, the drybacks will cause salt to accumulate very quickly. First thing it does is try to lock out potassium. Just helped a commercial client i do some consulting for with this exact issue on Monday. drying back coco is tricky and you really have to have the nutrient strength dialed or you end up flushing and adjusting like crazy. Backing to flowering nutes off a touch may help get her sorted. It’s not bad atm. Can test runoff to verify, but I think she’s running hot. Just my $.02
Good luck Getting them sorted. Nice flowers dude. Cheers

 

[flipflop64]

Thanks for your input mate
I've been trying 2.5EC for a few days but i think it actually made it worse
Buds are still quite fat but i dont want to have the same problem a third time
I'm in rockwool btw. Media EC at field capacity is 5.5-6 (substrate sensors)

Anybody else any ideas/input?

 

[Imzzaudae]

Stop pushing. These plants are far enough into flower that they only need about 15% of the nitrogen they did 3 weeks ago. You need to give her only P.K for 2 or 3 weeks. Let her use up the extra N in the pot.
Then calculate for 100ppm Nitrogen and watch the plant. let her take on fall colors.
You need to feed a good flowering mix once a week not twice a day.
What are you feeding? What medium in pots?

Mix up your flowering mix. Soak it to 25% runoff. Then let the plant dry out almost to wilt before feeding or watering again.

Plant's look nitrogen toxic but washed out with to much light.
What light are you using? How far above your plants canopy is the light?
Anything above 200w should be 30 inches above the canopy about 65% power setting.
Maybe 75% for flowering no higher!

This may help you as well. This is my flowering regiment. Some run a little longer some right on schedule.
It's up to you to keep an eye and make informed decisions.

 

[flipflop64]

Stop pushing. These plants are far enough into flower that they only need about 15% of the nitrogen they did 3 weeks ago. You need to give her only P.K for 2 or 3 weeks. Let her use up the extra N in the pot.
Then calculate for 100ppm Nitrogen and watch the plant. let her take on fall colors.
You need to feed a good flowering mix once a week not twice a day.
What are you feeding? What medium in pots?

Mix up your flowering mix. Soak it to 25% runoff. Then let the plant dry out almost to wilt before feeding or watering again.

Plant's look nitrogen toxic but washed out with to much light.
What light are you using? How far above your plants canopy is the light?
Anything above 200w should be 30 inches above the canopy about 65% power setting.
Maybe 75% for flowering no higher!

This may help you as well. This is my flowering regiment. Some run a little longer some right on schedule.
It's up to you to keep an eye and make informed decisions.

View attachment 2112895

I am in rockwool

 

[Imzzaudae]

Next time try 50% Vermiculite. 50% Peat Moss.
In a 5 gallon pot add
40 grams Dolomite lime = Magnesium and Calcium.
10 grams Gypsum. Sulfur and Calcium Mix well.
Vermiculite has Silica in it.
Check out this video.